Project Summary/ Abstract The long-term goal of the proposed research is to uncover molecular mechanism driving non-apoptotic cell death in vertebrate development and disease. Programed cell death functions to sculpt organs, remodel tissues, regulate cell number, and remove defective cells. While apoptosis is the most studied type of cell death, it does not account for all cellular destruction during development. Studies in C. elegans have uncovered a novel developmental cell death program, referred to as linker cell-type death (LCD), which is morphologically and molecularly distinct from apoptosis. Cell death with LCD features is commonly observed during vertebrate development and in patients and mouse models of neurodegenerative polyglutamine diseases. This proposal seeks to identify molecular events driving LCD in C. elegans, and to test their functional conservation in vertebrate settings. To rigorously investigate these mechanisms, this F32 proposal combines training in genetics, microscopy and computational analysis in vertebrate and invertebrate model systems to investigate the following specific aims: 1) identify molecular targets of the Ubiquitin Proteasome System (UPS) that precipitate cell destruction during LCD in C. elegans by performing functional studies and a yeast 2-hybrid screen; 2) uncover the molecular basis of LCD in vertebrates by developing a cell culture assay, testing roles of homologs of C. elegans LCD genes, and conducting a whole-genome CRISPR/Cas9 screen in cultured mammalian cells. The studies proposed here will lead to the development of new markers to distinguish among different types of cell death in vertebrate development and disease, while uncovering the molecular underpinnings of LCD. Because LCD is a prevalent type of cell demise, this proposal may not only shed light on basic aspects of development, neurodegeneration, and cancer, but could also eventually uncover in-roads of clinical significance.